linux-kernel - Re: [PATCH 7/8] firmware: vpd: remove platform driver

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Message-ID: <CAODwPW-5+yB1cHcFJhqkg+8-xLEk2L46h=89Ed7sPxyAtxeutg@mail.gmail.com>
Date:   Wed, 24 May 2017 17:04:41 -0700
From:   Julius Werner <jwerner@...gle.com>
To:     Guenter Roeck <groeck@...gle.com>
Cc:     Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Wei-Ning Huang <wnhuang@...gle.com>,
        Julius Werner <jwerner@...omium.org>,
        Guenter Roeck <groeck@...omium.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 7/8] firmware: vpd: remove platform driver

I'm not a kernel expert so maybe I don't understand this right, but...
I think this might have been done this way to ensure that the driver
can get initialized correctly regardless of probe ordering.
coreboot_table_find() may fail with -EPROBE_DEFER if the
coreboot_table driver and its dependent (coreboot_table-acpi or
coreboot_table-of) haven't been probed yet. In that case we want the
VPD driver to wait and try again later, after they've been probed. I
believe with the way this used to be written the driver core did that
automatically for us, but with your change I'm not sure if it still
does.

On Wed, May 24, 2017 at 10:22 AM, Guenter Roeck <groeck@...gle.com> wrote:
> On Tue, May 23, 2017 at 5:07 PM, Dmitry Torokhov
> <dmitry.torokhov@...il.com> wrote:
>> There is no reason why VPD should register platform device and driver,
>> given that we do not use their respective kobjects to attach attributes,
>> nor do we need suspend/resume hooks, or any other features of device
>> core.
>>
>> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
>
> One reason might be to use devm_ functions for memory allocations to
> simplify error handling and cleanup. Without that, I agree.
>
> Reviewed-by: Guenter Roeck <groeck@...omium.org>
>
>> ---
>>  drivers/firmware/google/vpd.c | 44 ++++++++++++++++---------------------------
>>  1 file changed, 16 insertions(+), 28 deletions(-)
>>
>> diff --git a/drivers/firmware/google/vpd.c b/drivers/firmware/google/vpd.c
>> index 78945729388e..f4766bf6785a 100644
>> --- a/drivers/firmware/google/vpd.c
>> +++ b/drivers/firmware/google/vpd.c
>> @@ -22,8 +22,6 @@
>>  #include <linux/kobject.h>
>>  #include <linux/list.h>
>>  #include <linux/module.h>
>> -#include <linux/of_address.h>
>> -#include <linux/platform_device.h>
>>  #include <linux/slab.h>
>>  #include <linux/sysfs.h>
>>
>> @@ -279,47 +277,37 @@ static int vpd_sections_init(phys_addr_t physaddr)
>>                 ret = vpd_section_init("rw", &rw_vpd,
>>                                        physaddr + sizeof(struct vpd_cbmem) +
>>                                        header.ro_size, header.rw_size);
>> -               if (ret)
>> +               if (ret) {
>> +                       vpd_section_destroy(&ro_vpd);
>>                         return ret;
>> +               }
>>         }
>>
>>         return 0;
>>  }
>>
>> -static int vpd_probe(struct platform_device *pdev)
>> -{
>> -       int ret;
>> -       struct lb_cbmem_ref entry;
>> -
>> -       ret = coreboot_table_find(CB_TAG_VPD, &entry, sizeof(entry));
>> -       if (ret)
>> -               return ret;
>> -
>> -       return vpd_sections_init(entry.cbmem_addr);
>> -}
>> -
>> -static struct platform_driver vpd_driver = {
>> -       .probe = vpd_probe,
>> -       .driver = {
>> -               .name = "vpd",
>> -       },
>> -};
>> -
>>  static int __init vpd_platform_init(void)
>>  {
>> -       struct platform_device *pdev;
>> -
>> -       pdev = platform_device_register_simple("vpd", -1, NULL, 0);
>> -       if (IS_ERR(pdev))
>> -               return PTR_ERR(pdev);
>> +       struct lb_cbmem_ref entry;
>> +       int err;
>>
>>         vpd_kobj = kobject_create_and_add("vpd", firmware_kobj);
>>         if (!vpd_kobj)
>>                 return -ENOMEM;
>>
>> -       platform_driver_register(&vpd_driver);
>> +       err = coreboot_table_find(CB_TAG_VPD, &entry, sizeof(entry));
>> +       if (err)
>> +               goto err_kobject_put;
>> +
>> +       err = vpd_sections_init(entry.cbmem_addr);
>> +       if (err)
>> +               goto err_kobject_put;
>>
>>         return 0;
>> +
>> +err_kobject_put:
>> +       kobject_put(vpd_kobj);
>> +       return err;
>>  }
>>
>>  static void __exit vpd_platform_exit(void)
>> --
>> 2.13.0.219.gdb65acc882-goog
>>

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